

with open('/Users/daidongyang/Downloads/text_xxx.html') as html_text:
    str = html_text.read()
    start = str.index('rnd')
    end = str.index('video_url')
    print(start, end)
    print(str[start+6: end-12])
    start = end
    end = str.index('postfix')
    print(str[start+12:end-12])